Project Summary Opioid Use Disorder (OUD) is a national epidemic and poses a high, growing mortality risk. Yet the majority of people with OUD do not seek treatment. Civil commitment (CC) to a short period of compulsory inpatient treatment is an increasingly common but largely untested policy for managing OUD and its mortality risk. It is currently unknown whether CC for OUD is effective in reducing opioid use and its mortality risk. If CC for OUD is effective, it would be an important and under-recognized means of addressing a critical public health concern. If, however, CC for OUD proves ineffective, its expanding use would be an unjust deprivation of liberty and wasteful of clinical and judicial resources. Thus, a full-scale prospective study of CC for OUD is needed. This R21 proposal will address two key challenges that must be overcome before such a study can be conducted. Aim 1 will test and refine recruitment and retention strategies to prepare for a full-scale prospective study of outcomes following CC for OUD. This Aim will yield effective strategies for recruiting committed and not-committed participants at the time of their CC court hearing, and for following them over a 3-month period. Aim 2 will determine whether evaluated-but-not-committed individuals can serve as a valid comparison group for a prospective study of outcomes from CC for OUD. We will evaluate the comparability of 100 committed vs. 100 not-committed individuals on key covariates that are directly related to the criteria used to justify a CC order. Using a three-step propensity-scoring procedure, these data will determine the sample size needed for an adequately powered prospective study of outcomes from CC for OUD.